Thanks for your warning, Bill. It's well taken and greatly appreciated.
Believe it or not, I essentially answered my own question shortly after I wrote that post. I had my existing 5V Mean Well HRPG-300 "overclocked" to about 5.9V -- very close to burning out the strips if the whole amount was getting through from the power supply. Given the voltage drops I was seeing I didn't think that was a problem, but then it occurred to me that if I was seeing only 2.6V across the strip when the strip was being run wide open, but wasn't otherwise noticing these sorts of brownouts when less white-intensive programs were running, it would probably be wise for me to see what kind of voltage was running through the strips when they were simply dark. Sure enough, when the strips are dark they show most of that voltage getting through -- I was seeing readings of around 5.8V on an otherwise dark and idle strip. Yikes.
So compensating for voltage drop with extra voltage is a bad idea -- got it. Scratch that from the playbook. I didn't quite earn my "blue smoke" patch but it sounds like I have been pushing my luck. I think I'm going to just resign myself to the idea that these strips are better suited to color patterns rather than being used for general area lighting, and leave it at that for now. There are programmatic ways to ensure that the overall color is even and consistent (i.e. not pushing them to DMX maximum), and I think I'm going to pursue that approach now that I'm re-injecting power throughout the system as has been suggested.
To answer your question about wiring, I am using CAT5 wiring throughout the system, with the exception of the initial feed coming in from the power supply to the controller. For that, I am using 18 gauge lamp wire. The SANDevices E682 (which is a GREAT little controller and soldering project for anyone who's into that sort of thing, by the way -- http://www.sandevices.com/
) is capable of supporting 16 separate channels of LED strips (I am not using all of them because of DMX limitations), so I am running channel pairs on each CAT5 cable. The controller feeds a 12-port ethernet patch panel (to facilitate connections rather than having to continuously plug and unplug the Phoenix connectors on the E682), which in turn feeds about 25-50' of CAT5 cable between the controller and the strips. On the other end I have something of a Frankenpatch, where I've connected a JST 4-pin cable to the back of a CAT5 port, which in turn feeds the strips themselves.
Do they get warm? I can't say I've noticed the cables, JST connectors or the strips getting warm at all, even after being on all day. The body of the CAT5 ports on the strip ends get _slightly_ warm, maybe a couple of degrees warmer than ambient. It's really subtle and because this rig is up near ceiling height I'm not always sure if it's just my imagination or they are generating a little heat.
In any case, having now thought about this more, and discovered how much voltage flows through the strips when they are idle, it seems reasonably clear to me that the voltage drop is coming from the inherent nature of these strips, not the system wiring. That 1) when all or most of the pixels are idle, nearly all the voltage gets through and we're only looking at a drop of .1V or so from the level measured at the power supply's outputs some 50' of cable away, and 2) when all or most of the pixels are showing full-value RGB white (255R, 255G, 255B), the combined draw of all the pixels is causing the voltage to drop by, in my case, nearly 3V. I would also note that the data and clock lines run on the same cable at the lower logic voltage of 3.3V, and am not seeing any sort of data or clocking problems at all. If this were a wiring problem wouldn't we expect to see data/clocking problems if those signals weren't properly arriving to the first pixel in the strip (after which, they are regenerated)?
I *AM* running some very long runs of CAT5 cable -- 50 feet or more -- but given the measured voltages when the strips are idle it seems pretty clear to me that the wiring is not the problem. Would you agree? Is the slightly elevated temperature of the connectors something I need to be worried about?
Rig picture, for the curious:https://www.facebook.com/photo.php?fbid=537591049606230&set=a.379752268723443.90952.188797797818892&type=1